This is a simple website that you can run locally that converts a StreamingHistory.json to endsong.json to use in scrobblify. Be aware that scrobblify has bugs and may or may not scrobble your whole file to last.fm, even though it will recognise it entirely.
Use git clone https://github.com/kostiskap1999/endsong-to-StreamingHistory-converter.git from your terminal to clone the project in a certain folder.
After changing the directory to the folder you cloned the project, use npm start to run it. Make sure you have npm installed. After a while, http://localhost:3000 will open, or you can open it manually to view the website in your browser.
Upload an endsong.json as the button prompts.
After clicking on 'Convert' the algorithm will generate an amount of StreamingHistory.json files which you can then download from the respective buttons that will appear. The reason it generates many files instead of one is because of a restriction in last.fm that only allows a user to scrobble as many as 2800 songs daily. Each StreamingHistory.json file has 2800 songs and is meant to be scrobbled at different days.